/Engine/Source/Editor/PropertyEditor/Public/DetailLayoutBuilder.h
If this is a sub-struct customization it will return those sub struct. Otherwise the root struct will be returned.
void GetStructsBeingCustomized ( [TArray](API\Runtime\Core\Containers\TArray)< [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FStructOnScope](API\Runtime\CoreUObject\UObject\FStructOnScope) > > & OutStructs ) const